Transcatheter aortic valve replacement (TAVR) is a proven strategy for the treatment of severe aortic stenosis that has been validated for use in patients who are not eligible for surgical aortic valve replacement (SAVR) due to patient frailty or associated high operative risk. TAVR with the use of a self-expanding or balloon-expanded bioprosthetic valve has been FDA-approved for commercial use in the US in selected patients. TAVR is rapidly becoming the method of choice to treat aortic stenosis in patients deemed to be at increased risk of death if offered a traditional surgical aortic valve replacement. Patients presently selected for TAVR, however, are most often elderly with frailty and a number of comorbidities. The femoral artery is generally the first choice for access to the aortic valve. In patients with significant arterial occlusive disease, however, marked tortuosity of the ileo femoral system and/or significant at risk atheromatous plaque within the native aorta and/or aneurysmal disease may present significant risk for femoral access such that alternate access TAVR is preferable. An alternative route has been proposed several years ago in the form of a trans-apical (TA) approach through the apex of the left ventricle exposed through a left lateral thoracotomy. The TA approach, however, requires opening the left chest in patients having potential pulmonary dysfunction and the rate of bleeding complications may be higher than that observed after traditional trans-femoral (TF) approach. In the search for yet another alternative to compromised peripheral arterial vascular access, a direct trans-aortic (TAo) route has been described in a limited number of cases since 2010. In a recent report, the cases performed through a TAo route represented only 4% of the TAVR cases performed by 2013.
Although results have been encouraging with TAVR, the risk of stroke has been demonstrated to be significantly higher with TAVR relative to SAVR. Clinically observed stroke (CVA) underestimates the prevalence of embolic events inherent with TAVR. During TAVR, stent and implanted valve expansion (with or without the use of a balloon) results in native valve compression and radial leaflet displacement that leads to the liberation of tissue and particulate matter that travels distally in the arterial tree. Some of the debris lodges in terminal branches of cerebral vessels and will be evidenced with new onset stroke. Other debris released at the time of TAVR lodge in vessels of the peripheral circulation, renal circulation, coronary circulation, and mesenteric circulation. These patients may manifest clinical scenario of renal failure, mesenteric ischemia, peripheral ischemia, and/or myocardial infarction. Other patients may not have acute clinical deterioration but may suffer late effects due to impaired functional reserve related to sub-clinical embolic events. The occurrence of embolic events during TAVR is a significant impediment to offering the technique to larger lower risk groups of patients.
A number of different approaches have been developed for embolic protection. Existing embolic protection devices are primarily adapted to deflect embolic material from the brachiocephalic vessels or capture embolic material within the brachiocephalic vessels. There are a number of difficulties with these existing embolic protection devices. First, deployment of the devices requires additional time and can conflict with the performance of the valve implantation procedure. Second, deployment of the devices may lead to additional vessel trauma and liberation of embolic material. Third, the deployment of the devices may be difficult and stability of deployment may make protection less than reliable. Fourth, the devices do not protect the brain from all sources of blood flow and particularly posterior cerebral blood flow is not filtered. Fifth, systemic embolization may still occur that may lead to intestinal, renal, and/or peripheral manifestations of ischemic gut, renal insufficiency and/or peripheral ischemia. Sixth, coronary embolization and myocardial infarction may occur due to proximal embolization.